Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Calorimeter
Patent
1993-06-30
1994-05-17
Housel, James C.
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Calorimeter
422 8212, 374 1, 374 31, G01N 2520
Patent
active
053125878
DESCRIPTION:
BRIEF SUMMARY
This invention concerns improvements in microcalorimeters. More especially, it concerns a microcalorimeter having a novel temperature sensing arrangement, offering improved stability and effective sensitivity.
Various designs of microcalorimeter are known and are available commercially. A flow microcalorimeter is described in UK Patent GB 1 366 886 and U.S. Pat. No. 3,467,501, the teaching of which is incorporated herein by reference. A particular use of such instruments is in the study of adsorption mechanisms, which may be done by ascertaining heats of adsorption and/or heats of desorption; heats of mixing, dilution, immersion and the like are also important sources of information for scientists and technologists and for the control of industrial processes and product quality.
In the microcalorimeter described in the above-mentioned UK Patent, the temperature changes in a bed of sample positioned within the microcalorimeter cell are detected by two glass-encapsulated thermistors in direct contact with the sample bed and reactants passed into the cell. These thermistors form two arms of a Wheatstone bridge circuit in which the remaining two arms are formed by two identical reference thermistors positioned in a metal block around the microcalormeter cell. Any imbalance in the output of the bridge by a change of temperature in the sample bed produces an electrical signal, which can be measured and evaluated.
Although the above-described arrangement has been very successful for some years, we have now discovered that an arrangement of temperature sensors more particularly described below, offers improved stability and effective sensitivity in the measurement of the very small heat effects studied in microcalorimeters. Accordingly, the present invention provides a microcalorimeter having a sample cell and means for retaining a sample within the cell, characterised in that the cell is of a fluorinated polymer which is insulating, and the cell has an inner wall defining a volume in which a sample may be positioned, and further characterised in that temperature sensing means are located within the polymer forming the cell. The sample in the cell may be placed directly in the form of a powder or granules, or may be inserted in a pre-charged cartridge or other suitable sample holder fitting into the cell. Fluids may then be percolated, either through the samples placed directly in the cell, or via the cartridge, as appropriate. Particularly preferred fluorinated polymers for the cell are PTFE in its various commercially available forms.
It is preferred to use as the temperature sensing means a thermistor, most preferably a pair of thermistors in a Wheatstone bridge circuit. Reference temperature sensors, preferably refence thermistors, are preferably also located within the polymer forming the cell, at a distance from the inner wall greater than that of the temperature sensing means. For example, in a cell formed from PTFE, the internal diameter of the cell may be from 3 to 10 mm, the temperature sensing means is/are located from 200 to 300 um, preferably from 200 to 250 um, from the inner wall, and reference sensors are located from about 1800 to 3000 um, preferably from 2500 to 3000 um, from the inner wall. It is surprising that temperature sensing means located within a material which is an efficient heat insulator should be effective, particularly when used in the preferred embodiments using reference temperature sensors. It will readily be appreciated that other temperature sensing means, for example thermocouples, may be used instead of thermistors.
In a preferred embodiment, a microcalorimeter incorporates an optional calibration unit. Such a unit comprises an electrical resistance heater element, capable of transferring heat to the interior of the cell upon passage of a known quantity of electrical energy, so that the microcalorimeter may be calibrated according to generally known principles. A new calibration unit is, however, unlike previous proposed units, capable of being retained in place during opera
REFERENCES:
patent: 3138436 (1964-06-01), Harmon
patent: 3467501 (1969-09-01), Groszek
patent: 3718437 (1973-02-01), Paloniemi
patent: 3972681 (1976-08-01), Clack et al.
patent: 4088447 (1978-05-01), Walker
patent: 4925315 (1990-05-01), Bonnard
Perry, R. H. "Teflon Heat Exchangers" in Perry's Chemical Engineers' Handbook, 6th ed., pp. 11-24, 1984.
Groszek Alexander J.
Templer Charles
Housel James C.
Microscal Limited
Snay Jeffrey R.
LandOfFree
Microcalorimeters does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microcalorimeters, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microcalorimeters will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-874891